Television receiver



vOct. 13, 1942. A. H. COOPER 2,293,870

TELEVISION RECEIVER Filed Dec. 12, 1940 Fi 1. Egg. 7

INVENTOR ATTORNEY Patented Oct. 13, 1942 asses-n TELEVISION Arthur HenryC 9)",

Industries Limited, Middlescx, England, a company 01 Electric & MusicalBritain Inglantanignnrto m Great Application December 12, 1940, SerialNo. 369,773 In Great Britain August 24, 1939 1 cum. (on 178-15) Thisinvention relates to television receivers and is concerned withimprovements in conditions under which the received pictures are viewed.It is. customary to exclude general external illumination from thescreen of the receiver in order to avoid loss of intensity ofillumination on the screen itself, but it is found that the strongcontrast between the illuminationbi the screen and the surroundingsemidarkness may cause eye-strain to viewers, particularly in a receiveremploying a cathode ray tube capable of giving a very brilliant picture.

,The main cause of eye-strain is not due to the viewer trying to discerna dim picture in a darkened room, but to observation of a bright picturein a room darkened so as to avoid refiections from the front It isimportant that light should not fall directly upon the viewing screen,and the object of the present invention is to lessen the sharp contrastreferred to and so to reduce or eliminate eyestrain, while avoiding lossof illumination of the screen itself.

According to the present invention in a television receiver or otherapparatus employing a cathode ray tube upon the luminescent screen ofwhich a pattern or picture is to be viewed, in order to reduce oreliminate eye-strain due to contrast between picture or patternbrilliance.

and the surrounding relative darkness, means are provided forilluminating the region behind said receiver or surroimding theluminescent screen of the cathode ray tube while avoiding detrimentalillumination of the luminescent screen.

The illumination, which may be said to form a background, may beeffective upon the walls behind and around the television receiver andmay conveniently be effected by one or more electric lamps arranged soas to be concealed within the receiver cabinet but projectingillumination throughthe back, sides or both of the receiver upon thewalls of the room or upon a screen provided for the purpose. Louvres maybe provided in the side walls or back of the receiver in order to permitcontrol of the degree of background illumination. Alternatively, or inaddition, the lamps may be controlled by a resistance to enable them toso to provide a soft yellowish tinge to the illumination.

Instead of arranging electric lamps to provide illumination upon thewalls behind or around the receiver, lamps may be arranged in suitablemasking devices to cause illumination upon the surface surrounding theluminescent screen of the cathode ray tube. Again, a member, such as aglass rod, surrounding the luminescent screen may be formed or treatedto cause dispersion of light from a lamp or lamps arranged of thecathode ray tube.

be under-run and at the endsgof the rod. Alternatively. the luminescentscreen of the tube may be'disposed within an aperture in a glass panelthe surface or which is treated asby grinding or stippling to causedispersion of light at the surface of the panel from a lamp or lampsarranged at one or more edges of the panel.

In order that the invention may be more clearly understood and readilycarried into effect, certain forms of apparatus embodying the inventionwill now be described in greater detail by way of example and referencewill be made to the forms shown in Figures 1. 2, 3 and 4 of theaccompanying drawing.

A television receiver equipped with a lighting arrangement in accordancewith one method of carryin out the invention is provided with a pair of40 watt lamps arranged in series and connected across the source ofsupply to the receiver. The lamps are fixed in holders at the back ofthe receiver so as to illuminate the walls in the region behind andimmediately around the receiver suiilciently brightly to light up thewhole room to an intensity at which viewers may move about freely, theillumination affording a broad border to the receiver.

In an alternative form of equipment a fairly high power lamp, forexample a watt lamp, mounted in a holder fixed to the rear of thecabinet is connected in series with the supply to the lamps used fornormal room lighting. when the receiver is not in use the 100 watt lampis arranged to be short-circuited and the lamps supplying the normalroom illumination are fully operative. When a switch serving toshort-circuit the 100 watt lamp is opened the region behind the receiveris illuminated by this lamp and, due to the insertion of the 100 wattlamp, the intensity of the illumination provided by the normal roomlight is reduced. Such an arrangement provides the required bright areain the neighbourhood of the receiver while there is suilicient light inthe rest of the room for purposes of comfort without involvingdetrimental illumination of the screen surface.

In order to avoid interference with the supply wiring at the point atwhich the receiver is connected, a suitable form of combined adaptorplug and switch with the necessary leads may be provided which willserve the purpose of connecting the 100 watt lamp in series with thelamps used for the room lighting when the receiver is in operation.

When one or more electric lamps are employed to illuminate the panelsurface surrounding the luminescent screen of the cathode ray tube, suchlamps are mounted within masking devices to ensure that theirillumination shall not fall directly upon the luminescent screen itself.

It is well known that if a source of light is placed at the edge of asmooth glass panel the light will mainly be transmitted through theglass and become visible at the edges. If the surface of the glass panelis scored or ground or marked by roughening the glass surface in theform of letters, etc., the latter will become luminous due to scatteringof the light at the scored surfaces. This principle may usefully beapplied in carrying out the present invention and for example a glassrod having its surface scored by one or more lines may be arrangedaround the edge of the mask of the receiver screen, the light from therod thus only appearing in the region about the edge of the mask. Insuch a case the electric lamp is mounted at the end or ends of the glassrod as shown in Figure 1 of the accompanying drawing.

In this figure a fragmentary panel I of a television receiver is shownhaving a cathode ray tube rod 3 surrounds that aperture. A line 4 isscored upon the surface of the glass rod so as to cause dispersion oflight along the length of the rod from a lamp 5 the front of which ismasked by a screen, not shown.

In Figure 2, three separate rods, 6, I and 8 are shown and three lamps9, l and II are mounted between the ends of these rods, each rod beingscored with a line 4 as in Figure 1.

Figure 3 of the drawing shows a glass panel l2 having an aperture i3 toreceive the luminescent screen of the cathode ray tube. The frontsurface of the glass panel is ground, scored or stippled in such amanner to cause dispersion of light from electric lamps of which two, l4and I5, are shown by way of example. In order to prevent the lighttransmitted through the panel from interfering with the luminescence ofthe picture screen, the embracing edge ii of the glass panel is suitablyblackened.

In order to make maximum use of the light from thelamps l4 and I5 theedge l6 may be made reflecting as by a layer of silver before theblackening is applied.

Glow discharge lamps may be employed instead of those of theincandescent type shown and further means operating in a manneranalogous to that of an automatic gain control arrangement may beprovided to cause the illumination provided by these lamps to vary inaccordance with picture brilliance so that there shall not at any timebe undue contrast between the picture brilliance and the brilliance ofthe surrounding illumination. i

In Figure 4 there is shown schematically the receiver I03 having anantenna I III for receiving television signals accompanied by sound. The

2 mounted within an aperture and a glass receiver may be of any of theconventional forms so as to provide both a sound output to feed the loudspeaker I01 and the picture'reproducing tube I09. As is well known,these receivers include an automatic voltage control I05. A portion ofthe automatically controlled voltage is fed to a suitable power supply3, which power supply supplies'a glow discharge lamp III. The AVCvoltage fed to the supply H3 is so poled that increases in signalincrease the voltage supplied'tothe lamp II I so that the brilliance ofthe surrounding illumination is in accordance with that of the picturebrilliance.

I claim:

1.; A television receiver comprising a cathode ray tube having aluminescent target area to be viewed, a masking surface surrounding thescreen and an illuminating means positioned adjacent the target area andsurrounding the masking surface in the area adjacent the target forilluminating the masking surface and thereby reducing contrast andeye-strain.

2. A television receiver comprising a cathode ray tube having aluminescent target area to be viewed, a masking surface having anaperture therein, and said target area being in register with saidaperture, an illuminating means positioned adjacent the target area andsurrounding the masking surface in the area adjacent the target areathereby reducing contrast and eye-strain.

3. A television receiver comprising a cathode ray tube having aluminescent screen area to be,

viewed, a masking surface having an aperture therein, said screen beingin register with said aperture, and means comprising a circular glassrod positioned adjacent said screen and surrounding said aperture forilluminating. said masking surface only, said glass rod being scored onthe surface facing said masking surface.

5. A television receiver comprising a cathode ray 'tube having a. lum'escent screen to be viewed, a masking surface having an aperturetherein, said screen being in register with said aperture, and meanscomprising a plurality of light sources and a plurality of transparentarctuate rods positioned adjacent said masking surface and surroundingsaid screen, said plurality of rods being scored on the surface "facingsaid masking surface.

6. In a television receiver the method of eliminating eye strain due tocontrast between picture brilliance and surrounding contiguous area ofdarkness, which comprises the steps receiving signaling energyrepresentative of a picture to be reproduced, deriving from the receivedsignaling energy other signals representative of the average brilliancyof the picture to be reproduced, illuminating the surrounding contiguousarea of darkness only, and controlling the intensity of the illuminationin accordance with the derived signals.

, 7. Television receiver comprising means to receive signalsrepresentative of a picture to be reproduced and accompanying soundsignals,.

ARTHUR HENRY COOPER.

for illuminating the masking surface and

